Screen structure



Feb. 8, 1938.

D. F. NEWMAN SCREEN STRUCTURE 'Filed April 1"?, 19:56

ATTORNEYS Patented Feb. 8, 1938 SCREEN STRUCTURE David F. Newman,Rockville Centre, N. Y., assignor to Trans-Lux Corporation, a,corporation of Delaware Application April 17, 1936, Serial No. 74,913

2 Claims.

My invention relates to a composite structure utilizable, if desired,solely as a screen for rear projection purposes. My invention also hasreference to a composite structure serving, if desired, in a dualmanner, i. e., as a rear projection screen and in connection with or asa part of a sound reproducing system. It shall be understood thatreferences in this specification and in the appended claims to a screenor projection screen shall be understood as generically comprehending ascreen utilizable solely for projection purposes or in connection with asound reproducing system as stated.

In accordance with my invention, a screen or composite structure of thecharacter stated comprises screen-forming material having associated,incorporated, or combined therewith fabric of a character not heretoforeused in the screen art and possessing advantages over those fabricswhich have been used in association with screenforming material.

Further objects, advantages and characteristics of my invention willbecome apparent from the following description.

My invention resides in the screen, composite structure, features andarrangements of the character hereinafter described and claimed.

This application is a continuation in part of my prior applicationSerial No. 512,533,.flled January 31, 1931, renewed September 1, 1933.

On the accompanying drawing:

Figure 1 is a View illustrating fabric of a character heretofore used inassociation with screen-forming material;

Fig. 2 is an enlarged plan view illustrating a section of a screen asconstructed in accordance with my invention; and

Fig. 3 is a vertical sectional view taken substantially on theline 3-3of Fig. 2 looking in the direction of the arrows.

My invention relates particularly although not necessarily to screens orcomposite structures of the character stated which comprise translucentscreen-forming or body material formed from gelatine and glycerine orother material as may be desirable and with vwhich there is associatedor incorporated a sheet of fabric of a type not heretofore used in thescreen art, such screens being adapted particularly for rear projection.

More particularly, the aforesaid body material may be of a characterknown to those skilled in the art. For example, such body material maycorrespond more or less with that disclosed in U. S. Letters Patent No.1,151,502, No. 12,231,727,

or No. 1,980,285, it being understood, however, that the use of some ofthe agents mentioned in said Letters Patent is optional depending uponthe use for which the projection screen is intended. As understood inthe art, the afore- 5 said body material may be so produced that itexists as .a mass of viscous material.

From the viscous material thus obtained, a sheet-like screen or screenstructure of suitable thickness may be produced in any suitable manner.Preferably, this is accomplished by a moldingoperation, a suitablematrix table embodying a plane surface of suitable material and extentor area being utilized for the reception of the mixture. The surface ofthe table should be bordered by a retaining wall of a heightsubstantially equal to the thickness of the screen or compositestructure to be produced and said table should be heated to suitableextent, preferably within a range somewhat below the tempera-ture of theaforesaid mixture.

After the matrix table has been brought to such suitable temperatureconditions as stated and with the aforesaid mixture in proper condition,the latter 'should be poured on or lap- 25 plied to the table,preferably until it slightly overflows the bordering wall thereof. Theexcess material should now be removed, as by application of a straightedge to the aforesaid retaining wall. 30

It has been proposed, in accordance with the disclosure of Troeger U. S.Letters Patent No. 1,216,380 to strengthen a screen with strands and,more particularly, these strands may be of silken thread. Further and inaccordance with the disclosure of U. S. Letters Patent No. 1,672,- 656to Arthur C. Payne, it is known that there may be associated withscreen-forming material a crinkly fabric and, more particularly, one ofirregular weave, as georgette crepe, such as is shown at G on Fig. 1 ofthe drawing.

Primarily, fabrics, as aforesaid, are utilized so as to prevent orimpede sag of -the screen when it is subjected to high and/or humidtemperature conditions. A fabric such as georgette crepe is reasonablysatisfactory for the intended purpose but this does not hold true underall conditions and circumstances. Such a fabric is of the interlacedstrand type and, if the width thereof exceeds '7G-inches ordinarily or92 inches as the usual highest limit, a sort of selvage as at a, Fig. 1,is formed by the weaving machinery when the width attains the valuestated above, this selvage extending longitudinally of the fabricwhereby the latter in a lengthwise zone is nor.-

.uniform as compared with the more uniform material at opposite sides ofsaid zone. -This selvage is not a true one inasmuch as it consistsmerely of an accumulation or closer grouping of the lengthwise strandsin the aforesaid lengthwise zone, it having proven impractical toovercome this condition due to mechanical limitations of commercialweaving machinery if the fabric widths exceed those stated above.

Aside from the primary defect noted above, interlaced strand fabric suchas georgette crepe is objectionable in a number of more or lesssecondary respects.

Thus, as indicated at b, Fig. 1, the fabric G may be more or lessirregular both longitudinally and transversely, such defects arising fora variety of reasons such, for example, as the improper handling orplacement of the delicate strands, the fact that such strands are apt tovary in diameter in different lengthwise zones, etc.

Further, as indicated at bl, Fig. l, commercially woven silk fabric ischaracterized by non-uniformity. More particularly, this non-uniformcondition is present both lengthwise and crosswise of the fabric andappears as a series of alternating light and dark bands of varyingwidths.

For ordinary non-screen uses, artificial fillers may be so associatedwith the fabric as to cause it to be of substantially uniformappearance, such artificial fillers rendering minor selvages and othernon-uniform conditions practically unnoticeable. However, as known tothe art and partly as hereinafter stated, fabrics to be used in theproduction of projection screens of the vcharacter herein describedshould be free from such artificial fillers and should also be as freeas possible of inherent foreign matter such as gums, resins, etc. Undersuch conditions, the association with screen-forming material, asdescribed above, of an irregular or non-uniform fabric such, forexample, as of the general character shown in Fig. l causes the screen,during projection, to be of non-uniform appearance since the selvagedand other irregular or nonuniform areas are dark and there is a markedcontrast between them and adjacent more truly uniform areas. Thiscontrasting appearance between adjacent screen areas, of course, isobjectionable.

I have determined that, as a substitute for fabric of the type describedabove, i. e., fabric of the interlaced strand type wherein the warp andfilling threads are disposed at right angles and are not twisted aroundeach other, there may advantageously be utilized knit fabric preferablyformed from silk strands as fabricated, for example, on any suitableknitting machine. Knit fabric as produced by such machines may bedimensionally larger, as regards width and length, than is required forrear projection screens, said fabric being of generally uniformcharacter throughout the area thereof in the sense that there is littleor no selvage or other non-uniformity such as indicated at a, b and blof the fabric G of Fig. l. In this specification and in the ap- Dend'edclaims, the term uniform, when used in a descriptive sense as regardsthe knit fabric, shall be understood as referring solely to the omissionof the above noted selvage or other nonuniformity from said knit fabric.Accordingly, when the dimensions of a desired screen are relativelylarge, a section of the above described knit fabric may be associatedwith the body material to thereby produce a screen which, during theprojection operation, does not exhibit non-unie formities such as existin the fabric G.

Accordingly, to construct the screen of my invention, a suitable sheetof knit fabric, such as indicated at K, Fig. 2, from which foreignmatter such as gums, resins, etc., has beensuitably removed should bestretched on a frame having an opening of such extent that it fitssnugly around the aforesaid retaining wall of the matrix table. Asshown, any given section of this knit fabric K is formed from strands sdisposed in looping relation as at t, this being customary in theknitting art.

After the excess screen-forming material has been removed from thematrix table as stated above, the sheet of knit fabric K is suitablylowered toward and into engagement with the upper surface of thematerial on the matrix table, care being taken to avoid entrapment ofair between the knit fabric sheet and the viscous material. In so doing,the frame holding said knit fabric sheet comes into position around theaforesaid retaining wall of the matrix table, and thereupon the knitfabric sheet sinks into or becomes associated with the viscous material.application of heat to the matrix table should be discontinued and,after a suitable cooling period, as two or three hours, has elapsed, aknife should be passed between the frame holding the knit fabric sheetand the retaining wall of the matrix table to sever said sheet from itsframe. There upon, the molded screen, now translucent to a desireddegree, may be removed from the matrix table in any suitable manner. Asindicated in Figs. 2 and 3, the operation thus described yields a screenwhich comprises a sheet of translucent At this time,

material M with which is combined the aforesaid sheet of knit fabric K.

Thereafter, the edges of the screen should be suitably bound, as bycanvas strips or the like adhesively or otherwise suitably securedthereto, the strips preferably being provided with eyelets. When thescreen is installed for use, a suitable frame should be provided and thescreen positioned therein under a suitable degree of tension, as by ropepassing through the eyelets and engaging the frame.

A screen constructed in accordance with my invention is durable andfunctions in an entirely satisfactory way for the display ofrepresentations to an audience. The knit fabric K functions in adesirable manner to reinforce the screen and to thereby prevent orimpede the aforesaid screen sag. In this connection, it seems that knitfabric, probably due to the different mesh characteristics, is morereadily or better associatable with the viscous screen-forming materialthan are the interlaced strand fabrics heretofore used in thisconnection. At the same time, the knit fabric is highly satisfactoryfrom the projection viewpoint. This follows because knit fabric of thetype described is of uniform character throughout and, as a result, thescreen, during projection, is not of streaked or other irregularappearance. In addition, it has been determined in practice that, in anunpredictable manner and for an unknown reason, sections of a sheet ofinterlaced strand fabric G do not always amalgamate or sink into thetranslucent body material when said fabric sheet'is lowered intoengagement therewith. This defect, when it occurs, is noticeable to amarked extent during the projection operation and renders the screenunsatisfactory for use. Experience has demonstrated, at least forscreens of small dimensions,

that the use of knit fabric K overcomes the difiiculty last noted. Thatis, such knit fabric K, throughout the entire area thereof, amalgamatesor sinks into the viscous body material to thereby produce a screen ofhighly desirable character from the projection viewpoint.

As hereinbefore stated, my invention has reference to a rear projectionscreen which, as well understood in the art, is disposed between theprojector and those viewing the images on said screen. With a rearprojection screen, the light passes through the screen during theprojection operation and, therefore, any imperfections such as thoseexisting in the sheet of interlaced strand `fabric G are in the visiblefield and hence objectionable. However, when the screen comprises asheet of knit fabric K, in lieu of the interlaced .strand fabric G, thescreen throughout the entire area thereof is of regular, uniformappearance, this, of course, being highly desirable.

It is well known in the art that interlaced strand fabric of thecharacter shown in Fig. 1 is one in which the warp and filling threadsare disposed at right angles to each other, the filling threads crossingthe warp threads in non-twisted relation such, for example, asillustrated in the aforesaid Letters Patent N o. 1,231,727. With asection of knit fabric as herein described, the strands are disposed ininterlooping relation as well understood in the knit fabric art. Itshall be understood that my invention as defined in the appended claimsis limited to a translucent screen which is properly light diffusive, asdetermined by the light-diffusive agent and the fabric sheet, for rearprojection practice and which comprises a sheet of knit fabric of thecharacter just described.

While the invention has been described with respect to a certainparticular preferred example which gives satisfactory results, it willbe understood by those skilled in the art after understanding theinvention, that various changes and modifications may be made withoutdeparting from the spirit and scope of the invention and it is intendedtherefore in the appended claims to cover all such changes andmodifications.

What is claimed as new and desired tobe secured by Letters Patent is:

1. In a projection screen, a sheet-like body of translucent material,and a sheet of uniform knit fabric combined with said body oftranslucent material, said translucent material and said sheet of knitfabric cooperating to form a screen properly light-diffusive for rearprojection practice, a substantial amount of light passing through saidknit fabric and the translucent material whenv the screen is included ina rear projection system.

2. In a projection screen, a sheet-like body of translucent materialformed principally from gelatine and glycerine, and a sheet of uniformknit fabric incorporated in said translucent material on one surfacethereof, said translucent material andsaid sheet of knitfabriccocperating to form a screen properly light-diffusive for rearprojection practice, a substantial amount of light passing through saidknit fabric and the translucent material when the screen is included ina rear projection system.

i DAVID F. NEWMAN.

